Prior art U.S. Pat. No. 5,279,123 mentions that shaped memory alloy (abbreviated to SMA) devices are well known in the art to undergo a martensitic (diffusionless) transition dependent upon the temperature applied to the SMA device. The SMA device when heated above its transition temperature undergoes a shape change to a memorized shape and when cooled below its transition temperature reverses the shape change from the memorized shape to an original shape. This change in shape can be used to provide mechanical work.
Often, as disclosed in prior art U.S. Pat. No. 5,459,544 issued Oct. 17, 1995, the SMA device is a metallic wire. When electrical current is applied to lead wires connected to opposite ends of the SMA wire, the SMA wire is heated to due to electrical resistance and it shrinks or contacts, i.e. recovers, to a memorized shape. When the electrical current is cut, the SMA wire cools to extend, i.e. deform, to an original shape.